Stomatal characteristics,conductance ratios,and drought-induced leaf modifications of semiarid grassland species

Seventeen greenhouse-grown grasses from the Nebraska Sandhills region were surveyed for foliar stomatal density and distribution, closed guard cell lengths, open stomatal apertures, and surface characteristics (using scanning electron microscopy), surface conductance (using a steady-state porometer), and drought-induced leaf modifications. Leaves of C₃ species exhibited a proclivity toward being amphistomatic or hyperstomatic, while C₄ species tended to be more hypostomatic. Leaf modification, when it occurred, resulted in the enshrouding of the adaxial surface. Conductance data showed functional amphistomaty in most species, revealing differential functioning of adaxial and abaxial stomata. Conductance patterns were not closely related to stomatal aperture per unit area leaf surface or to stomatal distribution patterns. Lowered adaxial: abaxial conductance ratios, increased stomatal density, reduced stomatal size, and less drought-induced leaf modification were seen in C₄ grasses as compared with C₃ grasses. C₃ range and C₃ meadow species did not differ in conductance ratios, density ratios, or stomatal size, although meadow species exhibited much greater drought-induced leaf modification. Postulations involving correlation of adaxial: abaxial conductance ratios to stomatal distribution patterns, and assumptions of stomatal distribution based upon habitat and/or photosynthetic pathway may be erroneous. These characteristics may be of limited usefulness as morphological indicators in the search for drought-tolerant ecotypes of prairie grasses.     

27种木犀属植物叶表皮微形态特征的研究

利用光学显微镜和扫描电子显微镜观察了27种木犀属植物的叶表皮,测量并统计了气孔器类型、气孔大小、气孔密度、气孔指数及腺点密度等指标,以明确各种的叶表皮细胞形状及垂周壁式样、表皮角质膜、蜡质纹饰及气孔外拱盖的具体特征。结果显示:木犀属植物叶下表皮有气孔器,形状为圆形、椭圆形;气孔器类型多为不规则型,只有总状桂花和狭叶木犀为环列型;气孔器外围角质层有放射状、条状、环状、颗粒状等多种类型;叶表皮细胞形状有无规则形和多边形2种;下表皮腺点的数目远远大于上表皮。研究表明,木犀属植物气孔器和叶表皮细胞特征在种之间差异比较明显,可以作为种间鉴定的重要依据,具有重要的分类学意义。     

14种木犀榄族植物叶表皮微形态的研究

利用光学显微镜和扫描电子显微镜对木犀榄族（Oleeae）5属14种植物的叶表皮微形态特征进行了观察,结果表明：（1）叶表皮细胞形状有无规则形和多边形两种;下表皮腺点的数目远远大于上表皮,流苏树上表皮细胞没有腺点;叶下表皮有气孔器,形状为圆形、椭圆形;气孔器均为不规则型;气孔器外围角质层有放射状、条状、环状、颗粒状等多种类型;（2）气孔器和叶表皮细胞许多特征具有明显的种间差异,可以作为种间鉴定的重要依据;（3）叶表皮微形态结构上的许多共同特征,表明木犀榄族植物是单独一自然类群。上述特征可为木犀榄族植物属及物种的划分与鉴定、系统演化关系的探讨等提供参考。     

Morphological characteristics of leaf epidermis and size variation of leaf, flower and fruit in different ploidy levels in Buddleja macrostachya (Buddlejaceae)

Buddleja macrostachya (Buddlejaceae) is a widespread shrub native to the Sino-Himalayan mountains and beyond. It has been found to occur at two ploidy levels, hexaploid, 2n=6x=114 and dodecaploid, 2n=12x=228. To determine if morphological characters might be used as indicators of ploidy levels, we measured floral and fruit length, relative and absolute leaf size, trichome density on both leaf surfaces, and stomatal density and length in different populations of B. macrostachya. In general, flower and fruit length, absolute leaf size, and stomatal length increased with an increase at ploidy level (P<0.01), whereas adaxial cell and stomatal density decreased with an increase at ploidy level (P<0.01). We found no conspicuous differences in relative leaf size (P>0.05) in different populations. Other characters studied such as trichome type, cuticular membrane and ornamentation of stomata, cell and stomatal shape, and anticlinal wall pattern were quite constant in this species. Thus it appears that flower and fruit length, absolute leaf size, and stomatal frequency and length can be used to distinguish hexaploid from dodecaploid cytotypes either in the field or in herbarium specimens.     

Distribution of stomata on the second leaf ofZea mays following root hypoxia

The changes in leaf dimensions, transverse and longitudinal gradients in stomatal density and the total number of stomata under the influence of root hypoxia were followed. In spite of considerably reduced leaf area following hypoxia the total number of stomata per leaf was not changed significantly. The resulting increase in stomatal density was not uniform being the most prominent in the basal part of the leaf where the distances between stomata and between rows of stomata became shorter.     

Kinetic characterization of reduced pyridine nucleotide dehydrogenases (duroquinone-dependent) in cucurbita microsomes

Stomatal conductances of normally oriented and inverted leaves were measured as light levels (photosynthetic photon flux densities) were increased to determine whether abaxial stomata of Vicia faba leaves were more sensitive to light than adaxial stomata. Light levels were increased over uniform populations of leaves of plants grown in an environmental chamber. Adaxial stomata of inverted leaves reached maximum water vapor conductances at a light level of 60 micromoles per square meter per second, the same light level at which abaxial stomata of normally oriented leaves reached maximum conductances. Abaxial stomata of inverted leaves reached maximum conductances at a light level of 500 micromoles per square meter per second, the same light level at which adaxial stomata of normally oriented leaves reached maximum conductances. Maximum conductances in both normally oriented and inverted leaves were about 200 millimoles per square meter per second for adaxial stomata and 330 millimoles per square meter per second for abaxial stomata. Regardless of whether leaves were normally oriented or inverted, when light levels were increased to values high enough that upper leaf surfaces reached maximum conductances (about 500 micromoles per square meter per second), light levels incident on lower, shaded leaf surfaces were just sufficient (about 60 micromoles per square meter per second) for stomata of those surfaces to reach maximum conductances. This `coordinated' stomatal opening on the separate epidermes resulted in total leaf conductances for normally oriented and inverted leaves that were the same at any given light level. We conclude that stomata in abaxial epidermes of intact Vicia leaves are not more sensitive to light than those in adaxial epidermes, and that stomata in leaves of this plant do not respond to light alone. Additional factors in bulk leaf tissue probably produce coordinated stomatal opening on upper and lower leaf epidermes to optimally meet photosynthetic requirements of the whole leaf for CO₂.     

Leaf morphological and ultrastructural performance of eggplant (Solanum melongena L.) in response to water stress

The effects of water stress on leaf surface morphology (stomatal density, size, and trichome density of both adaxial and abaxial surfaces) and leaf ultrastructure (chloroplasts, mitochondria, and cell nuclei) of eggplant (Solanum melongena L.) were investigated in this study. Higher stomata and trichome densities were observed on abaxial surface compared with the adaxial surface. Compared with well watered (WW) plants, the stomata and trichome density of the abaxial surface increased by 20.39% and 26.23% under water-stress condition, respectively. The number of chloroplasts per cell profile was lesser, the chloroplasts became round in a shape with more damaged structure of membranes, the number of osmiophilic granules increased, and the number of starch grains decreased. The cristae in mitochondria were disintegrated. The cell nuclei were smaller and the agglomerated nucleoli were bigger than those of WW plants. Our results indicated that the morphological and anatomical responses enhanced the capability of plants to survive and grow during stress periods.     

Stomatal distribution patterns change according to leaf development and leaf water status in <Emphasis Type="Italic">Salix miyabeana</Emphasis>

Salix is a pioneer woody plant genus characterized by a strong plasticity in leaf morphology. The aims of this paper were to determine stomatal distribution (1) in mature leaves in response to environmental conditions, and (2) during leaf development. Stomata of abaxial and adaxial faces of mature leaves of Salix miyabeana SX67 (cultivated in short rotation coppice) were analyzed at the end of summer 2012 and 2013 at six locations in Quebec, Canada. Within each site and across the two growing seasons, stomatal density of abaxial faces was diluted by an increase in area of mature leaves due to higher rainfall. For shrubs with more than one growing season, stomatal density of abaxial faces was affected by annual rainfall, independently of site, whereas leaf area was predominantly influenced by site but was also modulated in part by rainfall. The number of stomata per leaf was site-specific, independently of rainfall. These leaves were mainly hypostomatic, although those collected on shrubs during their first growing season after coppicing (i.e. with a high root:shoot ratio) were amphistomatic. Similarly, at early development stages (surface area <2.8 cm²), leaves were amphistomatic, whereas stomata on adaxial faces of larger leaves were occluded. Nevertheless, stomatal conductance of abaxial faces increased with leaf area, whereas stomatal density was best described by a quadratic relationship. This strategy allows for a maximum uptake of carbon while limiting water loss during leaf development and to adapt the morphology of mature leaves depending on moisture and site conditions.     

Photosynthesis and Stomatal Conductance of Potato Clones (Solanum tuberosum L.) : Comparative Differences in Diurnal Patterns, Response to Light Levels, and Assimilation through Upper and Lower Leaf Surfaces

A few potato clones, such as A6948-4, had higher rates of photosynthesis in the field than the Russet Burbank and were able to maintain higher rates not only during mid-day but also in the early morning and late evening hours. In addition, they maintained higher carbon assimilation rates over a range of photosynthetic photon flux density from 400 to 2,000 microeinsteins per square meter per second.

Stomatal conductance increased linearly as irradiance increased from 500 to 2,000 microeinsteins per square meter per second with all four potato clones that were examined. Obviously, comparative measurements of stomatal conductance or diffusive resistance with potato must be taken at a known and constant photosynthetic photon flux density.

The upper (adaxial) leaf surface of some potato clones provided a surprising contribution to total carbon assimilation. Neither stomatal conductance, number of stomata per unit area, total area of the stomatal apparatus, nor chlorophyll content appear to account for differences in carbon assimilation rates among clones.

     

Comparative Epidermal Ultrastructure of Cotton (Gossypium hirsutum L.) Leaf, Bract and Capsule Wall

Cotton leaves are more physiologically active than the bractand the capsule wall of the fruiting structures. To elucidatethe disparities in their physiological behaviour, epidermalcell density, stomatal index, stomatal size, trichome densityand type, and epicuticular wax ultrastructure of cotton leaf,bract and capsule wall were delineated using scanning electronmicroscopy (SEM). The epidermal cells of the outer periclinalwalls on both surfaces of the leaf and bract were raised andconvex. Conversely, the capsule wall epidermal cells were polygonalwith flat outer periclinal walls. The stomatal complex in theleaf and bract was paracytic, whereas in the capsule wall thestomatal complex was anomocytic. The adaxial and abaxial stomataof the leaf were coplanar to the epidermal surface, as opposedto the raised adaxial stomata on the bract. On the contrary,the stomata on the capsule wall surface appeared to be slightlysunken. Furthermore, the capsule wall stomata were larger thanthe stomata on either surface of both the leaf and the bract.The stomatal index was greater on the abaxial surfaces of theleaf and the bract (18.4 and 9.4, respectively) than their correspondingadaxial surfaces (14.4 and 4.7, respectively). Leaves had thehighest stomatal index followed by the bract and the capsulewall. The indumentum consisted of glandular and nonglandulartrichomes, the density of which was greater on the abaxial surfacesthan on the adaxial surfaces of the leaf and bract. The capsulewall indumentum lacked nonglandular trichomes. Epicuticularwax occurred in the form of striations. However, the striationpattern varied among the organs. This study clearly illustratesmorphological disparities in the epidermal features of leaf,bract and capsule wall, helping to explain their physiologicaldivergence. Copyright 2000 Annals of Botany Company Gossypium hirsutum, epicuticular wax, raised stomata, scanning electron microscopy, stomatal index, trichomes     

Association genetics,geography and ecophysiology link stomatal patterning in Populus trichocarpa with carbon gain and disease resistance trade‐offs

Stomata are essential for diffusive entry of gases to support photosynthesis, but may also expose internal leaf tissues to pathogens. To uncover trade‐offs in range‐wide adaptation relating to stomata, we investigated the underlying genetics of stomatal traits and linked variability in these traits with geoclimate, ecophysiology, condensed foliar tannins and pathogen susceptibility in black cottonwood (Populus trichocarpa). Upper (adaxial) and lower (abaxial) leaf stomatal traits were measured from 454 accessions collected throughout much of the species range. We calculated broad‐sense heritability (H²) of stomatal traits and, using SNP data from a 34K Populus SNP array, performed a genome‐wide association studies (GWAS) to uncover genes underlying stomatal trait variation. H² values for stomatal traits were moderate (average H² = 0.33). GWAS identified genes associated primarily with adaxial stomata, including polarity genes (PHABULOSA), stomatal development genes (BRASSINOSTEROID‐INSENSITIVE 2) and disease/wound‐response genes (GLUTAMATE‐CYSTEINE LIGASE). Stomatal traits correlated with latitude, gas exchange, condensed tannins and leaf rust (Melampsora) infection. Latitudinal trends of greater adaxial stomata numbers and guard cell pore size corresponded with higher stomatal conductance (g_s) and photosynthesis (A_max), faster shoot elongation, lower foliar tannins and greater Melampsora susceptibility. This suggests an evolutionary trade‐off related to differing selection pressures across the species range. In northern environments, more adaxial stomata and larger pore sizes reflect selection for rapid carbon gain and growth. By contrast, southern genotypes have fewer adaxial stomata, smaller pore sizes and higher levels of condensed tannins, possibly linked to greater pressure from natural leaf pathogens, which are less significant in northern ecosystems.     

青藏高原和内蒙古高原典型草地植物叶片肾型和哑铃型气孔器气孔特征及其与环境的关系

该研究利用植物制片技术,以中国青藏高原和内蒙古高原典型草地常见种或优势种植物的叶片为研究对象,通过比较分析叶片哑铃型气孔器和肾型气孔器的特征及其与环境因子的关系,揭示植物叶片两类气孔器对环境因子的响应策略。结果表明:(1)叶片哑铃型气孔器气孔指标的变异系数小于肾型气孔器。(2)叶片哑铃型气孔器气孔指标与环境气候指标的关系弱于肾型气孔器。(3)叶片哑铃型气孔器气孔特征与环境关系在叶片上下表面之间存在显著差异,而肾型气孔器气孔特征与环境因子的关系在叶片上下表面之间无显著差异。(4)叶片哑铃型气孔器的气孔特征与降水关系密切,而肾型气孔器气孔特征与温度关系密切。(5)同一种气孔器的气孔特征在两个地区(青藏高原和内蒙古高原)间存在显著差异。研究认为,肾型气孔器和哑铃型气孔器的气孔特征及其与环境之间的关系存在差异,在分析气孔特征时有必要将肾形与哑铃形保卫细胞形成的气孔器加以区分,该研究结果有助于进一步理解中国草地植物叶气孔特征对气候变化的响应与适应策略。     

Leaf epidermal micromorphology of Cercis (Fabaceae: Caesalpinioideae)

The micromorphology of leaf epidermal cells and stomata of all eight species and one form (11 samples) of Cercis were observed by scanning electron microscopy and light microscopy. Both the adaxial and abaxial epidermal cells are polygonal or irregular in shape; the anticlinal walls are straight and arched or undulate. Two types of stomata, which occur only on the abaxial surface of the leaves, are found in the genus. The atypical paracytic type is present in only one species, Cercis chingii, and the anomocytic type is present in all other species. Interspecific differences are minor in the genus with regard to leaf epidermal characters, except for C. chingii, which is characterized by atypical paracytic‐type stomata, a two‐lipped outer stomatal rim, the highest stomatal density and undulate and densely pitted anticlinal walls in the adaxial epidermis. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 539–547.     

Ontogenetic changes in stomatal size and conductance of sunflowers

The ontogenetic changes in stomatal size, frequency and conductance (g_s) on abaxial and adaxial leaf surfaces of sunflower plants (Helianthus annuus L. Russian Mammoth) were examined under controlled environmental conditions. The stomatal frequency on the adaxial and abaxial leaf surfaces decreased with leaf ontogeny and insertion level. The ratio of adaxial to abaxial stomatal frequency did not change with leaf ontogeny and insertion level, and 42–44% of total stomata was apportioned to the adaxial surface. Ontogenetic changes in stomatal pore length were detected and increased with ontogenesis. The stomatal length of both leaf surfaces had linear relationships with leaf area. Ontogenetic changes in g_s were similar between the two surfaces. However the adaxial g_s was lower than abaxial g_s in leaves of higher insertion levels. Conductance had a linear relationship with width x frequency but not with pore area.     

Insertion Profiles in Stomatal Density and Sizes in Nicotiana Tabacum L. Plantlets

Tobacco (Nicotiana tabacum L. cv. Samsun) plantlets were cultured in vitro on Murashige-Skoog medium photoautotrophically (without sucrose) or photomixotrophically (with 3 % sucrose) under two irradiances [70 or 230 µmol m^–2 s^–1]. Significant differences in stomatal density and sizes in leaves of different insertion levels (3^rd, 5^th and 7^th leaves from bottom) in photomixotrophic plantlets but not in photoautotrophic ones were found after 35 d of culture. Stomatal density was higher in upper leaves and on abaxial leaf side. Higher irradiance enhanced stomatal density in photoautotrophic plantlets. Stomatal sizes decreased with leaf insertion level but no significant differences between leaf sides were found. Abaxial stomata were more circular than the adaxial ones. In photomixotrophic plantlets stomata tended to be more elongated in the 3^rd and the 5^th leaves, whereas stomatal elongation in photoautotrophic plantlets was similar in all leaves.     

中国梅花草属植物的叶表皮特征及其系统学意义

利用光学显微镜和扫描电镜对梅花草属Parnassia 30种植物的叶表皮进行了观察。结果表明:气孔器普遍存在于叶的下表皮,少数种的上表皮也有分布,均为无规则型。叶表皮细胞形状为多边形或不规则形;垂周壁式样可区分为近平直、浅波状和波状。在扫描电镜下,叶表皮气孔器外拱盖内缘为近平滑、浅波状或波状;一些种的保卫细胞两端有加厚;角质膜条纹状,有的条纹隆起,有的条纹上附有颗粒或小孔穴。气孔器类型及下表皮细胞形状的一致性表明梅花草属是一个自然分类群;sect. Saxifragastrum叶表皮特征具有多样性显示该组可能是一个复合群;突隔梅花草P. delavayi属于subsect. Xiphosandra,其气孔下陷,与其细胞学特征相似,支持独立为一组;此外,气孔器的分布、保卫细胞两端加厚、气孔器外拱盖内缘形态以及角质膜等特征对该属部分种的区分有一定的参考价值。     

高粱、紫苏叶脉密度与光合特性的关系

叶脉是植物叶片光合作用水分输送的重要结构。为阐述叶脉与光合特性之间的关系,以C4植物高粱(Sorghum bicolor)、C3植物紫苏(Perilla frutescens)为实验材料研究了叶脉密度和光合特性之间的关系。结果表明,与紫苏相比,高粱叶片叶脉密度大,导水能力强,蒸腾速率高,但气孔密度小。进一步分析表明,高粱叶片近轴侧气孔密度占总气孔的比例明显高于紫苏。叶脉密度大的高粱具有较高的净光合速率;而紫苏叶脉密度小,净光合速率也较低。由此表明,较高的叶脉密度有利于支持较高的光合速率,但研究表明叶脉密度和气孔密度可能不存在严格的协同变异关系。研究结果对理解植物光合作用适应有重要意义。     

地黄叶和茎的解剖学及组织化学研究

采用解剖学和组织化学方法对地黄叶和茎的显微结构以及梓醇、多糖的分布进行观察研究,以明确梓醇和多糖在地黄叶和茎中的分布特征。结果显示:(1)地黄叶的上、下表皮均分布有腺毛和非腺毛,腺毛都属于头状腺毛,包括长柄和短柄的头状腺毛,两类腺毛的分泌物化学成分主要是黄酮和多糖;叶的上、下表皮上都分布有无规则型气孔,下表皮的气孔密度比上表皮的大,但气孔指数相差不大;栅栏组织由2～3层薄壁细胞构成,排列紧密,海绵组织薄壁细胞形状无规则,细胞间隙大。(2)组织化学研究表明,海绵组织中黄斑样的薄壁细胞是梓醇和多糖的贮存场所,这类薄壁细胞在叶片边缘的齿末端处最为集中,茎的皮层、韧皮部和木质部的薄壁细胞也都是梓醇和多糖的贮存场所。     

Stomata and Structure of Tetraploid Apple Leaves cultured in Vitro

Leaves of anther-derived tetraploid apple (Malus pumila Mill.)shoots were examined by low-temperature scanning electron microscopy(LT-SEM). Leaves were serrate and wide with an undulating adaxialsurface due to convex epidermal cells, apparently without crystallineepicuticular wax. Stomata were absent from the adaxial surface,except for the marginal teeth which exhibited 40-60 stomataper leaf; they probably originated from residual mitotic activity.One third of abaxial stomata was occluded by the residual cuticleof the mother guard cell across the stomatal pore which rupturedwhen the stomata became functional. The stomatal index was 7·2(± 1·6) with 60-75 stomata mm^-2, i.e. abaxialstomata of tetraploid leaves expanded in vitro were less frequentthan those in triploid leaves either cultured in vitro (475-575stomata mm^-2) or grown on the tree (320-390 stomata mm^-2) wherethe stomatal index was 21 (± 4). Freeze-fracture transsectionsshowed that the tetraploid in vitro leaves were composed ofa layer of adaxial epidermal cells, followed by a single layerof palisade cells and four to five layers of spongy mesophyllcells and the abaxial layer of epidermal cells, in contrastto juvenile seedling-grown apple leaves in which the two layersof palisade cells comprised the majority (52-60%) of the leafvolume. The same morphological features, such as wide and lesspointed leaves, reduced stomatal density and stomatal index,and increased stomatal size that were previously reported fortree-grown tetraploid leaves were also expressed in vitro. Thus,causes of the stomatal deformation in tissue-cultured Rosaceaeare interpreted to be in part genetic and not purely environmental.Copyright1994, 1999 Academic Press Malus pumila Mill., apple, biotechnology, breeding, cryo-preservation, CO₂, juvenile, low temperature-scanning electron microscopy (LT-SEM), micropropagation, ploidy, stomata, tissue-culture, transpiration     

Stomatal Response to Light of Solanum pennellii, Lycopersicon esculentum, and a Graft-induced Chimera

To learn how species differences in stomatal behavior are regulated, the response of epidermal and leaf diffusive resistance to light was investigated in Lycopersicon esculentum Mill., Solanum pennellii Corr., and a periclinal chimera having an S. pennellii epidermis and an L. esculentum mesophyll that was produced from a graft of the two species. S. pennellii has about 23% fewer stomata per square millimeter than does L. esculentum, and the two species have contrasting stomatal sensitivities to light. The abaxial stomata of L. esculentum open in dimmer light and to a greater extent than the adaxial stomata. The abaxial and adaxial stomata of S. pennellii respond similarly to light incident on the adaxial epidermis and are less open at all quantum flux densities than comparable stomata of L. esculentum. The patterns of response to light of the abaxial and adaxial stomata of the chimera were practically identical to those of L. esculentum, and quite unlike those of S. pennellii. Thus, the pattern of stomatal light response in the chimera was regulated by the L. esculentum mesophyll. The reduction in stomatal frequency of the chimera, which was regulated by the epidermis of S. pennellii, contributed to the 40% difference in leaf diffusive resistance between the plants in moderate light.